Implement backspace on Buffer

spec/atom/buffer-spec.coffee

@@ -69,6 +69,31 @@ describe 'Buffer', ->
         expect(buffer.getLine(3)).toBe originalLine.substring(27)
         expect(buffer.getLine(4)).toBe lineBelowOriginalLine
 
+  describe ".backspace(position)", ->
+    it "can remove a character from middle of line", ->
+      originalLineLength = buffer.getLine(1).length
+      expect(buffer.getLine(1).charAt(6)).toBe 's'
+      buffer.backspace({row: 1, col: 7})
+      expect(buffer.getLine(1).charAt(6)).toBe 'o'
+      expect(buffer.getLine(1).length).toBe originalLineLength - 1
+
+    it "can remove a character from the end of the line", ->
+      originalLineLength = buffer.getLine(1).length
+      expect(buffer.getLine(1).charAt(originalLineLength - 1)).toBe '{'
+      buffer.backspace({row: 1, col: originalLineLength})
+      expect(buffer.getLine(1).length).toBe originalLineLength - 1
+      expect(buffer.getLine(1).charAt(originalLineLength - 2)).toBe '{'
+
+    it "can remove a character from the begining of the line", ->
+      originalLineCount = buffer.getLines().length
+      originalLineLengthFromAbove = buffer.getLine(11).length
+      originalLineLength = buffer.getLine(12).length
+      expect(buffer.getLine(12).charAt(0)).toBe '}'
+      buffer.backspace({row: 12, col: 0})
+      expect(buffer.getLines().length).toBe originalLineCount - 1
+      expect(buffer.getLine(11).charAt(originalLineLengthFromAbove)).toBe '}'
+      expect(buffer.getLine(11).length).toBe originalLineLengthFromAbove + originalLineLength
+
   describe ".save()", ->
     describe "when the buffer has a path", ->
       filePath = null

spec/atom/editor-spec.coffee

@@ -218,7 +218,7 @@ describe "Editor", ->
       expect(editor).not.toMatchSelector ':focus'
       expect(editor.hiddenInput).toMatchSelector ':focus'
 
-  fdescribe "when text input events are triggered on the hidden input element", ->
+  describe "when text input events are triggered on the hidden input element", ->
     it "inserts the typed character at the cursor position, both in the buffer and the pre element", ->
       editor.setPosition(row: 1, col: 6)
 
@@ -230,7 +230,7 @@ describe "Editor", ->
       expect(editor.getPosition()).toEqual(row: 1, col: 7)
       expect(editor.lines.find('pre:eq(1)')).toHaveText editor.getCurrentLine()
 
-  fdescribe "when return is pressed", ->
+  describe "when return is pressed", ->
     describe "when the cursor is at the beginning of a line", ->
       it "inserts an empty line before it", ->
         editor.setPosition(row: 1, col: 0)

src/atom/buffer.coffee

@@ -41,6 +41,13 @@ class Buffer
         start: {row, col}
         end: {row, col}
 
+  backspace: ({row, col}) ->
+    line = @lines[row]
+    if col == 0
+      @lines[row-1..row] = @lines[row - 1] + @lines[row]
+    else
+      @lines[row] = line[row..col] + line[col + 1..]
+
   numLines: ->
     @getLines().length